SPECIAL FEATURES

Engine Timing

Timing Chain Failure

In recent years there has been a definite trend of car manufacturers moving back to timing chain engine design. Timing chain set-ups are generally very reliable provided the engine oil is changed regularly.

However, over time a chain can stretch to beyond its tensioner’s adjustment capability at which point it will rattle. From this point the engine's timing may become erratic and cause cam and crank sensor fault codes; if the vehicle continues to be driven, the chain can snap causing similar damage to that of a snapped timing belt.

Some modern cars are suffering with premature failure of their timing chain assembly. The 1248cc Multijet engine is one such example and is fitted to a number of popular vehicles such as the Ford KA and the Vauxhall Corsa.

The Problem

Timing chain failure on the JTD Multijet engine is not unusual. Snapped chains on cars under three years old and with as little as 40,000 miles on the clock is an unfortunate reality for some owners.

A common reason for this failure appears to be that the bolts securing the tensioner work their way loose. This slackens the chain which either rattles for a while before snapping, or sometimes fails very quickly with little or no notice. Lubrication, oil feed and low oil pressure due to lack of servicing and the wrong oil, can also cause chain and tensioner issues.

The Symptoms

Failures frequently follow the same pattern:

The chain starts to rattle on cold start-ups which can lessen as the engine warms up. Being a diesel, the noise often goes unnoticed by the driver who thinks it is normal and carries on driving. The noise worsens until one of two things happens…

The chain jumps a few teeth, which has a marked effect on engine power and performance, at which time the driver no longer ignores the problem and takes it to a garage for repair

The chain snaps and the vehicle arrives at the garage on the back of a recovery truck

The Result

Chain failure can result in anything from a replacement chain kit, to substantial damage to the top of the engine – cylinder head, camshafts, valves and rockers.

When replacing the timing chain, there are other items that should be replaced as a matter of course. For example, the timing cover gasket and crankshaft oil seal are both perishable, and if the failure was caused by the original tensioner bolts working their way loose, then the vibrations may have damaged the threads. Either way, it is good practice to replace them as well.

Different to most suppliers, Blue Print’s timing chain kit contains not only the ‘standard’ components (chain, camshaft and crankshaft sprockets, both chain guides and the hydraulic tensioner), but also the timing cover gasket, crankshaft oil seal and timing tensioner bolts. Plus in order to do the job properly, the technician will need a specific engine locking and timing tool, so Blue Print also supplies a complete tool kit for the 1248cc JTD Multijet engine. The tool has been specifically designed to work with all Fiat, Vauxhall, Suzuki, Alfa Romeo and Ford applications. It can also be used as a replacement tool for the cylinder head, head gasket set and bolts, camshafts, valves, rockers, tappets, glow plugs and of course the oil filter if the engine has suffered heavy damage.